Middle Cambrian Gogiid Echinoderms from Northeast Spain: Taxonomy, Palaeoecology, and Palaeogeographic Implications
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Middle Cambrian gogiid echinoderms from Northeast Spain: Taxonomy, palaeoecology, and palaeogeographic implications SAMUEL ZAMORA, RODOLFO GOZALO, and ELADIO LIÑÁN Zamora, S., Gozalo, R., and Liñán, E. 2009. Middle Cambrian gogiid echinoderms from Northeast Spain: Taxonomy, palaeo− ecology, and palaeogeographic implications. Acta Palaeontologica Polonica 54 (2): 253–265. DOI: 10.4202/app.2008.0010 Gogia parsleyi Zamora sp. nov. and Gogia sp. are described from two different echinoderm assemblages, both from the middle Cambrian of the Murero Formation (Iberian Chains, NE Spain). Gogia parsleyi is reconstructed and described on the basis of fifteen complete or partial specimens and numerous isolated plates. It is characterised by spiralled brachioles, simple epispires, sometimes covered by stereomic domes or tiny cover plates, and by thecal plates arranged in subregular circlets. This gogiid population comprises juveniles, advanced juveniles and mature individuals. The material was found in the upper part of the Murero Formation (upper Caesaraugustian–lower Languedocian). Gogia sp. is represented by two almost complete specimens and several isolated plates from the lower part of the Murero Formation (lower Caesar− augustian). The genus Gogia was first described in Western Gondwana from the Languedocian (upper middle Cambrian) of France, but the material from Spain is older and represents the oldest record of this genus in Gondwana, suggesting an early migration from Laurentia. The gogiids are well preserved in two echinoderm Lagerstätten, which, together with other echinoderms, comprise the majority of the fossil fauna. Both levels are derived from obrution deposits produced in calm and open marine conditions, sometimes affected by sporadic storms. Their holdfast morphology suggests that these gogiids were low−tier suspension feeders, living attached to trilobite fragments in a soft, muddy environment. Key words: Echinodermata, Eocrinoidea, Gogiida, Cambrian, Murero Formation, Spain. Samuel Zamora [[email protected]] and Eladio Liñán [[email protected]], Área y Museo de Paleontología, Departa− mento de Ciencias de la Tierra, Universidad de Zaragoza, E−50009 Zaragoza, Spain; Rodolfo Gozalo [[email protected]], Departamento de Geología. Universitat de València.C/ Dr. Moliner n° 50. E−46100 Burjasot (Valencia), Spain. Introduction of Bohemia (Barrande 1887; Fatka and Kordule 1984, 1991), France (Ubaghs 1987) and China (Zhao et al. 1994, 2007, Echinoderms are an important component of middle Cam− 2008; Parsley and Zhao 2006). brian fossil assemblages from North Western Perigondwana. At present, only two complete and articulated eocrinoid Two problems restrict their study: (i) complete and articu− taxa are known from the Cambrian of Spain, Alanisicystis lated echinoderms are rare; and (ii) isolated plates have lim− andalusiae Ubaghs and Vizcaïno, 1991 (Fig. 1) and Ubaghsi− ited taxonomic value, usually only assignable to class level cystis segurae Gil−Cid and Domínguez, 2002. The first is from or above (Donovan and Paul 1982). Of the eleven echino− the lower Cambrian of the Ossa Morena zone (South Spain). derm classes recorded worldwide from the Cambrian (Sprin− It was originally included as a subgenus within the genus kle 1976), one of the most common is the Eocrinoidea Jaekel, Gogia, but certain features (for example the stereomic domes 1918. This Linnaean class is a paraphyletic group that com− covering complex epispires) suggest a taxonomic position prises stem−group members of the better known blastozoan independent of, but closely related to Gogia. The second, clades (Sprinkle 1973; Smith 1984; Paul 1988). Major ana− Ubaghsicystis segurae, comes from the middle Cambrian of tomical innovations of the eocrinoids include the develop− the Cantabrian zone (North Spain). It is the oldest articulated ment of erect brachioles for feeding and a long multiplated eocrinoid, with a xenomorphic stem composed of holomeric stalk, and later, a columnal−bearing stem to elevate the theca columnals (Gil−Cid and Domínguez 2002); these features sug− above the sea floor (Sprinkle and Collins 2006). gest a derived position amongst Cambrian eocrinoids. In addi− Among eocrinoids, representatives of the family Eocrini− tion to these complete eocrinoids, isolated plates belonging to dae Jaekel, 1918 are the most common, primarily from Lau− the eocrinoid Rhopalocystis? mesonesensis Clausen, 2004 rentia (Sprinkle 1973). Only a few fossils from Gondwana are from the upper lower Cambrian of the Iberian Chains, the considered as eocrinids. These are from the lower Cambrian of enigmatic blastozoan Eocystites sp. (Gil−Cid and Domínguez Spain (Ubaghs and Vizcaïno 1991), Morocco (Nardin 2006) 1998) from the middle Cambrian of Ossa Morena zone (South and China (Zhao et al. 2007), and from the middle Cambrian Spain), indeterminate eocrinoid plates (Álvaro and Vennin Acta Palaeontol. Pol. 54 (2): 253–265, 2009 DOI: 10.4202/app.2008.0010 254 ACTA PALAEONTOLOGICA POLONICA 54 (2), 2009 for respiration, biserial brachioles and an expanded, probably short holdfast for attachment to hard substrates. The aims of this paper are twofold, firstly to describe new taxa from Spain, and secondly to analyse the geographic and stratigraphic dis− brachioles tribution of gogiids. Some preliminary data on the palaeoecol− ogy of eocrinoids and other echinoderms from the Murero Formation is also discussed. Institutional abbreviation.—MGM, Museo Geominero, Ma− drid, Spain; MPZ, Museo de Paleontología, University of Zaragoza, Spain. Geological setting and stratigraphy The Murero Formation is exposed in several Cambrian local− ities (Fig. 2) in the Iberian Chains (NE Spain), all of which are rich in trilobites, echinoderms, brachiopods, and Burgess Shale−type fossils. Trace fossils are also present. Two large anal pyramid Palaeozoic outcrops trending NW−SE, separated by the Ter− tiary Calatayud−Teruel basin, constitute the central part of the Iberian Chains. In this region, Palaeozoic rocks are struc− tured into three tectonostratigraphic units, the Mesones Unit, Herrera Unit and Badules Unit (Gozalo and Liñán 1988), and theca Cambrian rocks are common in all three. The Cambrian stratigraphy of the Iberian Chains was es− tablished by Lotze (1929); the lithostratigraphic nomencla− ture has subsequently undergone minor modifications (Lotze 1958, 1961; Schmitz 1971; Liñán et al. 1992; Álvaro 1995). The units in this sequence (in ascending stratigraphic order) are: the Bámbola Formation, Embid Formation, Jalón For− mation, Ribota Formation, Huérmeda Formation and Daroca 5mm Formation for the lower Cambrian; the Mesones Group (Val− holdfast demiedes, Mansilla and Murero formations) for the lower– middle Cambrian; and the Acón Group for the middle Cam− Fig. 1. Holotype (MGM2005K) of gogiid echinoderm Alanisicystis andalu− brian–Furongian. The palaeontological contents of each unit siae Ubaghs and Vizcaïno, 1991 from the lower Cambrian of the Ossa were summarised by Liñán et al. (1996, 2002) and Gozalo et Morena zone (South Spain). Photograph of latex cast whitened with NH4Cl. al. (2008). The fossils described herein came from two different local− 1997) from the middle Cambrian (Mansilla Formation, Ibe− ities, Murero and Purujosa villages; both are situated in the rian Chains) and columnals of uncertain affinity from the Badules unit, which is considered to be the prolongation of the Furongian (Acón Group, Iberian Chains) (Zamora et al. in West Asturian−Leonese Zone to the southeast (Fig. 2A). They press), have also been described. are from two different beds in the Murero Formation. This for− Echinoderms from the Murero Formation are extremely mation represents a monofacial deposit of green lutites with diverse, with a long and complete fossil record (Zamora et al. interbedded carbonate nodules and very fine sandstones. The 2007), but few have been formally described so far (Friedrich original sediments were deposited in a shallow marine envi− 1993; Zamora and Rahman 2008). In this paper we report two ronment (sublittoral facies, sensu Liñán 1995). The Dyctio− new gogiid eocrinoids from the middle Cambrian Murero For− nina–Acrothele brachiopod assemblage is well represented mation. Gogia parsleyi Zamora sp. nov. and Gogia sp. are the throughout the formation and indicates the predominance of first representatives of the group reported from the Iberian low−energy deposits (Liñán and Mergl 2001). Chains. Gogia sp. is also the oldest representative of this genus The presence of agnostoid and polimeroid cosmopolitan in Western Gondwana and suggests taxa migrated to Gond− trilobites suggests an outer sublittoral facies for the Murero wana from the Laurentian palaeocontinent. Formation. These eocrinoids possess some plesiomorphic (primitive) Locality 1.—Murero is a small village situated on the west− characters, including an irregularly plated theca with larger ern branch of the Iberian Chains, located 80 km south of primary and smaller secondary plates, epispires (sutural pores) Zaragoza (Fig. 2B). The Cambrian rocks in this area show a ZAMORA, GOZALO, AND LIÑÁN—CAMBRIAN GOGIID ECHINODERMS FROM SPAIN 255 Moncayo Jarque Fault Herrera Unit Badules Unit Mesones Unit Precambrian rocks Tablado Range Tabuenca Borobia Purujosa Zaragoza Mesones de Isuela La Almunia de Da Godina Calatayud - Teruel Basin Calatayud Datos Fault Puig Moreno Herrera de los Villafeliche Navarros oo Murero Long. W 005 Long. 000 Badules C OC Daroca WAL GC Lat. N 41o Iberian Chains ELA OM Calamocha 200 km SP 010km Pre-Hercynian